BLA.CKMAN: THE SPERMATOGENESIS OF SCOLOPEND1IA. 7 



spermatocyte resembles the egg cell still more. It has become much 

 enlarged, and by its growth the cytosome has increased greatly, and out 

 of proportion to the nucleus. Thus, even in size, the spermatocyte at the 

 completion of the growth period resembles the egg. The elements within 

 the nucleus have become so arranged that this space is now occupied by 

 a very fine reticulum of granular liuin, which is no more dense than the 

 cytoplasm outside the nucleus and stains in a similar manner. All the 

 chromatin has apparently been withdrawn from this network and is now 

 contained in a large, peripherally placed, nucleolus-like body, which stains 

 in such a manner as to leave no doubt wdiatever as to its richness in 

 chromatin. From the striking resemblance of the cells at this time to 

 egg cells during the stage of the germinative vesicle I have called this 

 the pseudo-germinal vesicle stage of the spermatocyte, but shall in future 

 call it simply the " vesicle " stage. 



During all the growth period the centrosomes can generally be found 

 in these cells and can, indeed, be identified at all stages from the pro- 

 phase of the last spermatogonium up to the formation of the spermatozoon. 

 During the growth period they are contained in a centrosphere of slightly 

 modified archoplasm, which is often readily distinguishable from the 

 remaining archoplasm of the cell. Throughout the following division 

 the chromatic and archoplasmic structures behave in a manner similar 

 to that often recorded of egg cells daring the maturation and cleavage 

 stages. Indeed, the division figures resemble those characteristic of 

 cleavage stages much more closely than they do the maturation mitoses 

 of eggs. This is of course to be expected, since here there is to be an 

 equal division of the cytoplasm. 



During the changes following the beginning of the growth period there 

 arise what are apparently two types of spermatocytes. These are prob- 

 ably produced by differences in the environmental conditions surround- 

 ing the different cells. That they result in the formation of fundamentally 

 different kinds of spermatozoa, is very improbable when we consider their 

 later behavior. They, however, show notable differences at various 

 stages, and it is therefore convenient to recognize the two kinds. The 

 cells of the larger type resemble egg cells much more closely than do 

 those of the small type. This is true both as regards general appearance 

 and specific behavior. 



Xot only are the division figures of these spermatocytes very similar 

 to those of the female germ cell, but the cells arising by these divisions 

 are also at first very similar. The nuclei of the second spermatocyte 

 and the spermatids are peculiarly like the female pronucleus and the 



